1. Field of the Invention
The present invention relates to a device for realizing a logical operation, and is more particularly concerned with a device for carrying out a logical operation with one or more logical variables (A.sub.1, A.sub.2 . . . A.sub.n) given which the logical variables can be input in the form of control signals.
2. Description of the Prior Art
Binary circuits with which logical operations of the bivalent propositional logic are realized are devices, for example, of the type initially cited (v. in that regard, for example, the book "Binare Schaltkreise, Aufbau - Methoden - Anwendungen" by Walter Wolfgarten, Dr. Alfred Huthig-Verlag, Heidelberg, 1972). A logical variable which can only assume the two truth values "true" or "false" in the bivalent Boolean logic system is represented in these circuits by a logical variable which can assume switching states, for example, the "on" or "off" position of an on/off switch, corresponding to the two truth values. A logical operation to be carried out with one or more logical variables, the logical operation clearly assigning a truth value of a dependent logical variable to each truth value of the logical variables or, respectively, to each possible set of truth values of the plurality of logical variables and which may therefore be characterized by and is likewise characterized by a so-called truth table in which every possible value or set of values of the independent logic variables and the assigned value of the dependent variables are entered, is determined by a corresponding logic function dependent on corresponding logic variables which can be characterized by a switch state table corresponding to the truth table.
In the electronic binary circuits most frequently employed today, the switch states are given by, for example, two voltage values from two separate voltage ranges H and L which, for example, correspond to the values "true" and "false", respectively, of a logical variable. Therefore, given these electric binary circuits, a logical variable is represented by a binary electrical signal representing the corresponding logical variable. Each signal representing an independent logical variable can be input into the circuit over a, preferably, separate input and the signal representing the dependent logical variable is available at the output of the circuit.
Particularly familiar examples of such binary circuits are, among other things, the negator, the AND element, the OR element, the NAND element and the NOR element. The negator is an example of a binary circuit in which the logical operation can be carried out with only one independent logical variable. Every logical operation realized by the other cited elements is to be executed with at least two independent logic variables which can generally be input as signals over parallel inputs.
A primary desire, given devices of the type initially mentioned, is in further shortening the operation time, i.e. the time duration in which the logical operation s to be carried out. Given binary circuits, the operation time is predominantly determined by the switching time, i.e. by the time interval which is required for a transition from one switch state into the other switch state. Given the fastest binary circuits known today, which are realized by means of certain electronic binary circuits, switching times are achieved which lie in the nanosecond range and which can no longer be significantly improved for technological reasons. Moreover, these switching times appear additively in the realization of complicated logical operations, so that the operation times can lie far above the switching times given such circuits.